OK, been there, done that! Last fall/winter/spring I grew toms in a greenhouse. I used larger pots - 7 gallons, but they were spaced about one foot apart, both in rows and in the middle of the GH, between rows.

Can't say I had a great harvest, but... and a big but....

The plants grew great in October, November and early December. I had hundreds of blooms, nice foliage, the whole gamut (I did trim bottom leaves off, and had a fan). But then the sun drought came and in eight weeks time, I had maybe 20 hours of sunlight. Just as the sun emerged, I listened to some weather forecasters who said the high temp for the day would be 48 degrees and it would be mostly cloudy the entire time. Wrong - it turned very sunny and the temps got into the low 60s. Cooked my plants.

But to answer your question, if a plant is in its own container, and you provide the right soil mix and nuits, no reason why you need more than a foot per plant.

Again, I got tons of tomatoes
I presume this is hyperbole! At least 4,000 pounds from your plants? (Tons is at least two).

Where are you located?

I am in East Texas...low 60's? Cooked plants??? It was 82 degrees here the other day and mine didn't cook...

On warm days though I will prop the door open...and then close it all up at night.

I am on about the same level as Jacksonville, FL...

Here we get cold spells that can be days or even a week at a time...in the winter our days are nice sometimes... (mid 70s in January on occassion)....

It will get below freezing here especially at night, but it rarely freezes and stays frozen for any more than a few days at a time...extreme cases it will be below freezing for a week maybe.

And yes, tons = a bunch...not as in a literal ton.

I'm in Cincinnati. It was a day last spring. The weather forecast was for highs in the upper 40s and partly to mostly cloudy all day. When I left it was 42 degrees and mostly cloudy. A couple of hours later the sun came out and the temps soared to 60. Of course, I had not left the door open, not with the predictions.

By the time I finished my route and got home, the temps inside were 125 and I literally had dozens of fried green tomatoes, especially the smaller ones. Lots of the foliage suffered damage also.

If I was going to try gardening over the winter in the GH again, I would install one of those mechanical vents that open or close depending on the temps. But we have at least a month, sometimes six weeks when we are lucky to get six hours of sunshine per week!

I will use it for my seedlings this spring, though. 42 degrees won't harm seedlings so I can leave the door open if I need to.

Mike

Here is a link that might be useful: {{gwi:1396956}}

My experience differs. The same variety grown in a container vs one in the garden with proper spacing will producer earlier fruit but they will be smaller and less numerous plus if watering isn't carefully monitored the container plant won't be as healthy. Makes no sense to me to grow an indet plant in a container if you have garden space available unless earlier fruit is your main goal.

I started my container garden thing as an experiment. I did an in the ground garden my first year and was completely overwhelmed by weeds. It sucked. Bad.

Although this coming up year I will try an in the ground garden again most likely...but I will make use of weed cloth if I do.

Seriously, the last time, it was really bad.

For growing in my greenhouse though containers are a must.